Chemical and Physical Effects of Release Agents in the Formwork Process

The task sounds simple: Concrete and formwork should separate cleanly from one another after curing. What actually happens, however, is much more complex from both a chemical and physical standpoint.

Fresh concrete is alkaline, moist, and under pressure. It penetrates every uneven surface, reacts with surfaces, and tears away particles when the formwork is removed, unless a protective layer is present. A high-quality release agent prevents exactly that: It forms a chemical-physical barrier between the concrete and the formwork material, which prevents direct contact and actively protects the formwork material.

Damage caused by incorrect or missing release agents rarely becomes apparent after the first use. It accumulates until the formwork must be replaced prematurely.

In precast concrete plants, steel formwork is the standard, and particularly high standards for surface quality apply. The release layer must function reliably, but it must not be too thick. An oil film that is too thick, combined with a low-quality release agent, leaves pores and voids in the concrete component. In the precast concrete industry, this is not a cosmetic issue, but a quality defect.

Divinol release agents for steel forms are based on highly refined mineral oils with polar additives. The fatty acids they contain react with the calcium in fresh concrete to form insoluble lime soaps, which create a stable micro-release layer. The product is designed for residue-free release—no oil residues remain on the component when the formwork is removed. Its low viscosity ensures an extremely thin, uniform film on the formwork surface.

Road construction has different requirements than concrete construction, but the principle is the same: The release agent must function under real-world conditions without damaging the material.

Asphalt paving temperatures typically range between 130 and 180 °C. Rollers and pavers are in constant contact with hot bitumen. At the same time, it is essential to prevent the asphalt from adhering to the machine surfaces without chemically altering its structure.

On many construction sites, diesel is still used for this purpose. This is problematic for several reasons: Diesel chemically attacks the bitumen structure and softens the asphalt. It poses a health risk to workers through fumes and skin contact. And it can cause long-term soil contamination; in sensitive areas such as water protection zones, its use as a release agent is not permitted.

More release agent does not automatically mean more protection. Using too much can cause the concrete to lose aggregate. Too much oil on the formwork creates a soft, sandy surface on the finished component that does not meet quality requirements.

The solution is technically simple. After application, excess release agent should be removed with a rubber squeegee or a cloth. A thin, even film is perfectly sufficient and significantly more effective than a layer that is too thick. We provide application guidelines for all products that describe the correct application in detail.